1. Field of the Invention
This invention relates to filters of the type used to treat water to remove contaminants therefrom. The invention is also directed to a method of forming a part of the filter made from active carbon.
2. Background Art
Heretofore, filter cartridges for use in household water treatment apparatus, commonly referred to as water-treating units, or water-purifying units, have generally been constructed so that chlorine and organic matter are adsorbed by a particulate active carbon, whereas pollutants, rust, and bacteria of microscopic size are picked up by a hollow yarn membrane.
One exemplary filter cartridge has a cylindrical shape, with the interior of the cartridge partitioned into an active carbon-filled chamber and a hollow yarn membrane chamber. Water directed to the cartridge is first introduced to the active carbon chamber, which removes kalk- and mold-induced malodors from the water. The water is then delivered to the hollow yarn membrane chamber where other matter that is not removed by the active carbon is picked up by the hollow yarn membrane. An example of this type of filter is disclosed in Japanese Unexamined Patent Application Publication No. 10-85729.
An alternative construction, as disclosed in Japanese Unexamined Patent Application Publication No. 8-71541, has a cartridge filter with a tube formed from a hollow yarn membrane in the center thereof with an active carbon layer disposed over an outer peripheral surface thereof. Water to be filtered flows through the active carbon layer and then through the hollow yarn member, after which treated water flows out of the cartridge.
In each of the above filters, an active carbon is used in particulate form in a chamber partitioned with a membrane. This membrane has small diameter pores sized to pass water, but not the active carbon.
With both of the above filters, chlorine is removed mainly by the active carbon, with fine pollutant and turbidity removed by the hollow yarn membrane. Since little of the fine pollutant is removed as it is passed through the active carbon, the hollow yarn is prone to becoming clogged, which potentially leads to a shortened service life.
Another problem is that the hollow yarn membrane is relatively costly and takes up a large volume of the filter. If this type of filter is used in a water treatment system, such as one where it is directly attached to faucets, size and weight reduction become significant. Accordingly, the amount of active carbon that can be utilized may be limited by the required size of the hollow yarn membrane. Limiting the amount of active carbon may result in a shortened service life for the filter in removing chlorine, and the like.
Further, in a filter where a particulate active carbon is used, a water channel may be formed in the active layer as water is continuously directed therethrough. Once this channel is formed, the flowing water may be diverted through the channel, as a result of which the active carbon is only partially used during the filtering process. As a result, the filter may have a shortened life in terms of its ability to remove chlorine, and the like.
In Japanese Unexamined Patent Application Publication No. 2-17989, a water treatment filter is disclosed which has active carbon particles embedded in a porous, plastic matrix. This filter is designed so that the particulate active carbon can be used with a small particle diameter dispersed in the porous plastic matrix.
In U.S. Pat. No. 4,753,728, another filter is disclosed in which active carbon is set in a polymer. The polymer has a low melt index of less than 1.0 g/10 min (ASTM D13238, 190° C., 15 kg Load).
These last two filters are highly efficient since active carbon particles of small particle diameter can be used. The water flowing into the filter can flow through the entirety thereof, offering potentially a good service life in removing chlorine, and the like, with the active carbon.
However, these filters are deficient in that they are generally not capable of sufficiently removing fine pollutant from water and of adequately treating water that is highly turbid.
Further, the patent documents describing these last two filters do not disclose that these filters can be used on faucet-joined water-treating apparatus. The filters used on faucet-joined water-treating apparatus are preferably light in weight and small in size. Generally, with a filter having an active carbon dispersed in plastic, downsizing results in an inability to adequately remove chlorine, and the like. In the case of a filter for faucet-joined water-treating apparatus, a flow rate of water is desired to be around 2.0 to 3.0 L/min. By improving the ability to remove chlorine and the like, small diameter particulate active carbon has been found to impede the flow rate so that it is less than that desired.